In message , Martin Brown
writes
On 30/04/2019 11:34, Tim Lamb wrote:
In message , John
Rumm writes
On 30/04/2019 08:15, wrote:

How realistic are the manufacturers claims for energy produced by
their solar pv panels. If they claim 2kw howlikel is this to be
true/realistic ?

Its likely to be a true reflection of the maximum power delivery of
the panel when in full midday sun in the summer.

In peak summer you might get a load factor as hight as 20% in the
uk. In the winter it will be down in low single digits. Averaged
across the year its usually estimated to around the range of 10% -
12%. Also peak delivery never aligns with peak demand.
Hmm.. My grazing tenant is considering solar PV panels for an
unattended cattle watering set up.
12V bilge pumps seem readily available and adequate for the head and
flow required. Lead acid battery not a problem but...
how much panel do you need for Hertfordshire sunshine May to October?

It might be OK over that period with something like a 300W PV panel to
guard against several cloudy days in succession. The main worry will be
people nicking it - even the batteries grow legs sometimes
:-) 500m from the nearest highway. Trees grow along river banks so the
panel would probably go on the top of a 12 or 18ft. scaffold pole.
The battery/controller could be in a padlocked cabinet. I suppose some
sort of time delay would be required as a float over pressure switch
would reset as soon as the water had fed back through the pump. Non
return valve?

Hot weather conveniently requires more water which, last summer, was
around 600litres/day at a head of around 5m.
My mathmatical capabilities do not stretch to this sort of
problem:-)

mgh = 600kg x 10ms^-2 x 5m = 3000kJ needed each day

Roughly 8h daylight and 3600s in an hour = 29000s so in theory a 100W
panel would just be able to keep up if it was sunny every day but allow
at least twice that and you will need a charge controller too.
I suppose we need to consider pump motor efficiency.

Every time I have tried to do solar powered irrigation (but on a
slightly smaller scale) lugging a heavy SLA battery out to the field
and taking the old one away to recharge has won hands down. Solar
panels are a bit cheaper now but I doubt if it is truly worthwhile.
OTOH if he has a solar panel just lying around it would extend the
period between having to manhandle to battery and recharge it at home.

This is likely to be an annual requirement and the cost spread over
several years. It might be better to find a commercially available kit.

I only needed a 3m head of water and 100L delivered daily.

Hmm.. they could drink from the river if the general public had the
integrity to keep themselves and their dogs on the footpath.

Thanks


--
Tim Lamb